Re: [PATCH 4/4] sched/numa: Adjust imb_numa_nr to a better approximation of memory channels

Mel Gorman
2022-05-19T09:29:23Z

On Wed, May 18, 2022 at 06:06:25PM +0100, Mel Gorman wrote:
> I'm running the tests to recheck exactly how much impact this patch has
> on the peak performance. It takes a few hours so I won't have anything
> until tomorrow.
>

It wasn't my imagination, the last path was worth a few percent

v5.3 Min 95.84 Max 96.55 Range 0.71 Mean 96.16
v5.7 Min 95.44 Max 96.51 Range 1.07 Mean 96.14
v5.8 Min 96.02 Max 197.08 Range 101.06 Mean 154.70
v5.12 Min 104.45 Max 111.03 Range 6.58 Mean 105.94
v5.13 Min 104.38 Max 170.37 Range 65.99 Mean 117.35
v5.13-revert-c6f886546cb8 Min 104.40 Max 110.70 Range 6.30 Mean 105.68
v5.18rc4-baseline Min 110.78 Max 169.84 Range 59.06 Mean 131.22
v5.18rc4-revert-c6f886546cb8 Min 113.98 Max 117.29 Range 3.31 Mean 114.71
v5.18rc4-shiftimb3-v2r2 Min 95.34 Max 165.75 Range 70.41 Mean 120.92
v5.18rc4-consistimb-v2r2 Min 104.02 Max 175.22 Range 71.20 Mean 116.62
v5.18rc4-consistimb-revert-c6f886546cb8 Min 104.02 Max 112.56 Range 8.54 Mean 105.52

v5.18rc4-shiftimb3-v2r2 is patches 1-4
v5.18rc4-consistimb-v2r2 is patches 1-3

The last path is worth around 8% and is what's necessary to bring best
performance back to kernel v5.7 levels. As you can see from the range,
the result is unstable but reverting c6f886546cb8 reduces it by a lot.
Not enough to be at v5.7 levels but enough to indicate that the allowed
NUMA balance changes are not the sole source of the problem.

--
Mel Gorman
SUSE Labs